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4 <br />Schwartzwalder Mine -Hydrologic Evaluation of Mine Closure and Reclamation <br />Two other mines historically operated in Ralston Creek canyon. The Mena Mine is located about one mile <br />upstream from the Schwartzwalder Mine where the West Rogers Fault crosses Ralston Creek. The <br />Northstar Mine is located about one mile northwest of the Schwartzwalder Mine, in veins related to the <br />East Rogers Fault System. <br />2.2 Terrain <br />Ralston Creek flows from northwest to southeast across Section 25, and occupies a narrow, steep-sided <br />canyon, in the vicinity of the mine. Small intermittent tributaries of less than one mile in length enter <br />Ralston Creek from both the north and south directions in the west half of Section 25. In the east half, <br />short, usually dry gulches drain into Ralston Creek from the north (off the west side of Ralston Buttes) <br />while a steep ridge parallels the creek on the south. <br />The mine portal is located on the west side of Ralston Creek Canyon, and numerous mine facilities were <br />constructed on waste rock and fill from historical mining activities. <br />2.3 Climate <br />The Schwartzwalder Mine area has a semiarid climate characteristic of much of the central Rocky <br />Mountain region. Precipitation records from 1978 to 2007 at Ralston Reservoir (located about 2 miles from <br />the site and 560 feet lower in elevation) show a mean annual precipitation of 18.68 inches (Table 1). <br />Approximately 40 percent of the precipitation falls during the spring, much of it as wet snow. <br />Thunderstorms (June to August) account for an additional 30 percent of the annual precipitation. Fall and <br />winter are drier seasons, accounting for 20 and 10 percent of the annual precipitation, respectively. <br />Snowfall averages 68.8 inches per year, falling from late September through May. <br />Precipitation variation from the monthly and annual averages is shown in Table 2. With a standard <br />deviation of 3.64 inches, precipitation ranged from 15.0 to 22.2 inches during 68% of all years. The lowest <br />recorded precipitation was 11.9 inches in 2002 while the highest recorded precipitation was 26.4 inches in <br />1999. <br />Temperatures at the site are moderate. Extremely warm or cold weather is usually of short duration. Daily <br />summer temperatures ranges from 53 to 88 °F, and winter temperatures range from 23 to 46 °F, on average. <br />Table 1. Monthly Climate Summary at Ralston Reservoir <br />May 1, 1978 -June 30, 2007 <br />Jan -Feb -Mar A r ~ Ma -Jun Jul Au Se Oct = Nov Dec Annual <br />Average Max. 46.0:46.1: 52.3 59.4: 69.7:79.7 88.0 ~ 83.5 75.3:63.0 51.7 44.9: 63.3 <br />_ Temperature (F) _~ _ ............................._ ~-- ~.................. _...___..._ _ <br />Average Min. 23.6 : 22.9 ~ 28.9:35.0: 45.2 53.4:61.3: 58.3:50 3 39 3 29 1 23.6: 39.2 <br />Temperature, (F) - - - - `- <br />Average Total ! 0.61 s 0.65 1.87 ' 2.41 ~ 2.93 ~ 1.96 ` 1.64 2.13 € 1 38 1 22 ~ 1 13 0.75 ~ 18.68 <br />- ...---.-,-.-.. 3 ~ <br />Average Total 9.0 8.5 13.3 10.0 ~ 1.6 I 0.0 i 0.0 0.0 0.8 ' 3.1 11.6 10.8 68.8 <br />• 1 I _ _. _. _. _ <br />SnowFall (tn.) ~ I " ~ ~ <br />-------. <br />Average Snow 1! 1 1 1 0 0 0 0 0 0 1' 2 1 <br />De th in. <br />Source: Western Regional Climate Center (WRCC), data download for station 056816 (Ralston Reservoir, Colorado) <br />Percent of possible observations for period of record: Max. Temp.: 17.1% Min. Temp.: 17% Precipitation: 99% Snowfall: 98.9% Snow Depth: 98.7%. <br />Whetstone Associates • <br />4109B.071116 <br />